Microfluidics involves micro-scale devices that handle small volumes of fluids. Because microfluidics can accurately and reproducibly control and dispense small fluid volumes, in particular volumes less than 1 μl, application of microfluidics provides significant cost-savings. The use of microfluidics technology reduces cycle times, shortens time-to-results, and increases throughput. Furthermore, incorporation of microfluidics technology enhances system integration and automation.
Microfluidic reactions are generally conducted in microdroplets. The ability to conduct reactions in microdroplets depends on being able to merge different sample fluids and different microdroplets. A controlled modification of a chemical composition of the microdroplets is of crucial importance to the success of biochemical assays. Generally, conducting reactions in microdroplets involves merging a pair of pre-made microdroplets of different compositions, resulting in the formation of a mixed droplet that carries a mix of components needed for a particular assay. For example, in the context of PCR, a first droplet carries sample nucleic acid and a second droplet carries reagents necessary for conducting the PCR reaction (e.g., polymerase enzyme, forward and reverse primers, dNTPs buffer, and salts). Merging of the droplets produces a mixed droplet containing sample nucleic acid and PCR reagents so that the PCR reaction may be conducted in the microdroplet.
This mixing approach requires pre-emulsification of two liquid phases and a subsequent careful matching of pairs of the two different types of droplets for the purpose of achieving an optimal merge ratio of 1:1, which leads to sub-optimally merged droplets, and thus sub-optimal reactions or assays.